Routers form a central part of a data communication network and perform general routing of data packets. Headers in each packet control the route taken by that packet through the network. There can be multiple routers in a network. Information, as contained in the data packets, typically travels from one router to the next router, and eventually reaches the destination edge of the network, where a destination edge router receives the information packet and decides where it goes from there. Typically it goes to an Internet service provider at the opposite edge of the edge router. If the destination is a household PC, the Internet service provider then sends the information to the destination computer. If there is corporate access to the network, the information may go from the edge router directly to a corporate site.
A fabric is a collection of devices which cooperatively provide a general routing capability. Internet protocol (IP) routers require protection from fabric failures, for example optical fabric, packet fabric, and switch element fabric failures. The prior art uses duplicated switch fabrics and line cards that feed both switch fabrics simultaneously but receive from only one switch fabric at any given time.
Prior art designs based upon duplex or duplicated fabrics, while fully protecting from individual fabric failures, permit extensive loss of packets during a failure, detection, and protection event. In the prior art a line card receives output from one switch fabric, unless it detects a failure on that switch fabric, in which case it then spends about 50 milliseconds switching over to the redundant switch fabric. In an outage of a fabric, if it requires fifty milliseconds for the receiving line card to determine that a fabric is defective and to decide to start receiving instead from the redundant fabric, then all packets passing through that defective fabric during that fifty milliseconds are lost. The number of packets lost per line card is equal to the switchover time to the alternate fabric multiplied by the packet transmission rate through that particular switch fabric. Multiplying by the total number of line cards in the system, the result can be a huge amount of data lost during each 50 millisecond transient event, which creates a large impact on the network as a whole.
Needed in the art are a new system and method of IP router switch fabric protection that prevent or minimize loss of data packets during a fabric failure, detection, and protection event.